UNIVERSITY   OF   CALIFORNIA 

COLLEGE    OF    AGRICULTURE 

AGRICULTURAL   EXPERIMENT  STATION 

CIRCULAR  No.  266 
June,  1923 

ANALYZING  THE  CITRUS  ORCHARD  BY 
MEANS  OF  SIMPLE  TREE  RECORDS 

By  EOBERT   W.   HODGSON 


CONTENTS 

PAGE 

Introduction 1 

Orchard  Analysis 2 

Establishing  Tree  Identities 2 

Keeping  Production  Records 6 

The  Performance  Record 6 

Estimate  Records 6 

When  To  Make  Production  Estimates 8 

Estimate  Production  Record  Forms 8 

Segregation  into  Groups  According  to  Production 10 

Orchard  Efficiency 10 

Distribution  in  the  Orchard  According  to  Production 11 

Consistent  Performance  vs.  Inherent  Capacity 12 

The  Distribution  Chart 12 

Making  the  Distribution  Chart 13 

Environmental  Factors 14 

Inherent  Factors 16 

The  Tree  History  Record 17 

Tree  Inspection 17 

The  Tree  History  Record  Form 18 

Conclusion 20 

Summary 20 


INTRODUCTION 

The  factors  governing  success  in  the  raising  of  citrus  fruits  in 
California  may  be  divided  for  convenience  into  three  general  classes : 
those  determined  by  the  grower  in  the  cultural  practices  used;  those 
which  have  to  do  with  the  inherent  character  of  the  trees  themselves ; 
and  those  related  to  the  orchard  environment.  For  best  results,  the 
maintenance  of  an  optimum  combination  of  these  groups  of  factors 
is  required. 


Z  UNIVERSITY    OF   CALIFORNIA — EXPERIMENT    STATION 

Thus  far  the  factors  receiving  the  most  attention,  both  on  the 
part  of  the  grower  and  the  investigator,  have  been  the  cultural  prac- 
tices used,  and  it  is  gratifying  to  note  that  as  a  result  in  the  past 
decade  there  has  been  a  marked  increase  in  efficiency  on  the  part  of 
citrus  growers  in  the  application  of  such  practices  as  irrigation,  fertili- 
zation, pruning,  and  pest  and  disease  control. 

The  inherent  qualities  of  the  trees  have  also  received  considerable 
attention,  especially  during  recent  years,  with  the  result  that  much 
more  care  is  now  given  to  the  selection  of  stocks  and  bud-wood  than 
was  formerly  the  case. 

Beyond  the  general  questions  of  soil  and  climatic  limitations, 
however,  comparatively  little  attention  has  been  given  to  the  import- 
ant matter  of  the  orchard  environment  and  especially  its  relation 
to  cultural  practices.  Unquestionably  much,  if  not  most,  of  the  wide 
variation  in  the  yields  of  citrus  trees  is  due  to  differences  in  environ- 
mental conditions  as  related  to  cultural  practices  and  may  therefore 
be  overcome,  at  least  partially,  through  an  appreciation  of  this  fact 
on  the  part  of  the  grower.  It  is  certain  that  closer  attention  to 
this  class  of  factors  may  be  expected  to  materially  increase  the  effi- 
ciency of  the  average  citrus  orchard. 

OECHAED  ANALYSIS 

As  a  means  of  visualizing  the  relations  of  these  three  groups 
of  factors,  indicating  the  means  of  modifying  them  to  advantage, 
and  at  the  same  time  determining  the  relative  efficiency  of  the  orchard, 
a  method  of  analysis  is  herein  suggested  which  has  been  developed 
from  an  experience  of  five  years  of  such  work.  It  is  believed  that 
its  use  will  do  much  in  indicating  the  nature  of  the  causes  of  failure 
to  secure  satisfactory  yields,  and  also  ways  and  means  for  increas- 
ing the  production  of  the  average  orchard. 

ESTABLISHING  TEEE  IDENTITIES 

The  individual  tree  is  the  ultimate  unit  of  the  citrus  orchard, 
a  fact  not  sufficiently  appreciated  by  the  average  grower,  who  is 
accustomed  to  thinking  in  terms  of  acres.  The  change  in  attitude 
from  the  acre,  as  the  unit  of  production,  to  the  tree  is  necessary 
before  the  type  of  analysis  herein  suggested  can  be  undertaken.  The 
first  step  in  such  an  analysis,  therefore,  is  the  establishing  of  an 
identity  for  each  tree  in  the  orchard.  A  natural  and  logical  method 
is  that  wherein  each  tree  is  given  a  set  of  numbers,  which  not  only 
serve  to  establish  a  permanent  identity  but  also  to  designate  the 
location. 


Circular  266] 


ANALYZING   THE   CITRUS   ORCHARD 


The  system  most  commonly  used  consists  of  two  numbers,  the 
upper  giving  the  row  number,  and  the  lower  the  tree  number  (fig.  1). 
Where  a  large  acreage  is  involved,  divided  into  several  blocks,  it  is 
necessary  to  have  the  block  number  in  addition  to  the  row  number 
and  the  tree  number.     For  the  average  planting,  however,  the  block 


Fig.  1. — Showing  method  of  painting  numbers  on  tree  trunks.  The  uppov 
number  gives  the  row,  the  lower  number  the  tree.  Numbering  may  be  done 
either  by  use  of  stencils  or  free  hand. 


4  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

number  is  unnecessary.  For  convenience,  the  numbers  should  always 
be  placed  on  the  same  side  of  the  tree  and  at  about  the  same  height 
from  the  ground.  A  logical  and  recommended  system  of  numbering 
is  that  in  which  the  row  numbers  run  in  the  direction  of  flow  of  the 
water  in  the  standpipe  lines,  and  the  tree  numbers  in  the  direction  of 


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Fig.  2. — Diagramatic  sketch  showing  recommended  system  of  numbering 
rows  and  trees  as  related  to  irrigation.  Eow  numbers  follow  the  direction 
of  water  flow  in  the  pipe  lines;  tree  numbers  follow  the  direction  of  flow  of 
water  in  the  irrigation  furrows.  Numbers  are  always  placed  facing  the  direc- 
tion of  the  flow  of  water  in  the  irrigation  furrows. 


flow  of  the  water  in  the  furrows.  The  numbers  should  be  placed  on  the 
side  of  the  tree  facing  the  direction  from  which  the  irrigation  water 
flows,     (fig.  2.) 

The  most  commonly  used  method  of  affixing  the  numbers  is  paint- 
ing them  directly  on  the  trunk  or  on  a  main  branch  near  the  crotch, 
in  figures  from  two  to  three  inches  in  height,  using  a  thick  mixture 


Circular  266] 


ANALYZING   THE   CITRUS   ORCHARD 


of  white  lead  and  linseed  oil.  (fig.  1.)  If  the  bark  is  thoroughly 
cleaned  before  the  painting  is  done,  and  good  materials  used,  the 
numbers  will  last  for  many  years.  The  numbers  are  sometimes 
painted  on  small  boards  and  nailed  to  the  trunks  of  the  trees.  For 
young  trees,  stakes  with  the  numbers  painted  on  them  are  some- 
times used. 


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Fig.  3. — Tree  tag  combining  identity  and  location  record  with  estimate 
production  record.  Eead  down  the  tag  for  block,  row  and  tree  numbers. 
Numbers  are  the  same  on  reverse  side.    Block  8,  Eow  17,  Tree  24. 


Metal  tags  of  various  kinds  have  been  used  to  a  limited  extent  and 
also  water  proofed  paper  tags,  the  latter  usually  attached  to  the  outer 
shell  of  foliage  at  a  height  of  five  to  six  feet.  The  paper  tags  seem 
to  have  considerable  merit,  especially  tho  ;e  combining  tree  identity 
with  production  record,  which  will  be  referred  to  later,     (fig.  3.) 

The  cost  of  numbering  trees  is  small,  ranging  from  two  to  four 
cents  per  tree.  Painting  the  numbers  on  the  trunks,  either  by  means 
of  stencils  or  free  hand,  while  considerably  slower  than  tagging  the 
trees,  appears  to  have  fewer  disadvantages  than  any  other  system 
yet  devised. 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


KEEPING  PRODUCTION  EECOEDS 

The  keeping  of  production  records  is  of  fundamental  importance 
to  the  citrus-  grower,  fully  as  much  so  as  it  is  to  the  dairyman.  No 
progressive  dairyman  today  questions  the  value  of  the  cow-testing 
association.  The  fact  remains,  however,  that  very  few  citrus  growers 
keep  individual  tree  production  records.  The  keeping  of  tree  pro- 
duction data  is  necessary  to  the  carrying  out  of  the  method  of  orchard 
analysis  described  and  recommended  in  this  publication. 

The  Performance  Record. — In  determining  the  kind  of  records 
to  be  kept,  however,  the  object  for  which  the  records  are  required 
is  of  primary  importance.  Citrus  tree  production  records  may  be 
taken  for  two  purposes,  either  to  locate  and  test  high  producing  trees 
to  be  used  as  sources  of  bud-wood  for  propagation,  or  to  determine 
what  trees  are  consistent  low  producers.  In  the  case  of  the  first  object, 
it  is  of  course  obvious  that  as  accurate  records  of  quantity  and  quality 
of  fruit  as  can  be  secured  are  necessary,  even  though  the  getting  of 
such  data  involves  considerable  expense.  Emphasis  has  therefore 
been  placed  on  accuracy,  to  the  degree  of  securing  either  the  actual 
weight  of  fruit  produced  or  approximately  the  same  through  a  record 
of  the  number  of  boxes  and  half  boxes  picked.  The  tree  performance 
record  has  therefore  received  considerable  and  well  merited  attention. 

For  purposes  of  determining  low  producing  trees,  however,  and 
for  the  further  objects  of  arranging  the  trees  in  classes  according 
to  relative  production,  such  as  is  recommended  in  the  method  of 
analysis  herein  presented,  such  exactitude  is  unnecessary.  In  fact, 
the  very  trouble  and  expense  of  keeping  actual  tree  performance 
records  has  been  perhaps  the  principal  factor  in  deterring  citrus 
growers  from  undertaking  orchard  analyses. 

The  grower's  problem  is  to  determine  what  trees  consistently 
produce  only  fair  crops,  and  what  trees  are  regular  producers  of 
good  crops.  The  keeping  of  tree  performance  records,  with  the  pick- 
ing of  the  fruit  from  each  tree  separately  is  unnecessary  as  a  means 
of  securing  this  information. 

Estimate  Records. — The  estimate  production  record  is,  judged 
from  every  angle,  sufficiently  accurate  for  the  purposes  mentioned, 
and  is  in  addition  so  simple  and  practicable  as  to  leave  little  excuse 
for  failure  to  keep  production  records.  Actual  experience  has  shown 
that  not  to  exceed  two  days '  work  a  season  will  suffice  to  keep  estimate 
production  records  for  a  ten-acre  orchard. 

A  number  of  methods  of  estimate  production  record  keeping  have 
been  used.     Many  growers,  from  long  practice,  have  become  expert 


Circular  266]  ANALYZING   THE  CITRUS   ORCHARD  7 

in  estimating  production  in  field  boxes  and  with  little  effort  can  go 
through  the  orchard,  taking  two  rows  at  a  time,  estimating  the  pro- 
duction per  tree  in  boxes  with  remarkable  accuracy.  Picking  fore- 
men are  usually  expert  in  this  practice  and  for  a  small  additional 
sum  to  their  wages  are  usually  willing  to  make  such  estimates.  This 
method  is  far  simpler  and  less  expensive  than  the  tree  performance 
record,  and  may  be  used  successfully  for  orchard  analysis  purposes. 
It  does  not,  however,  differentiate  between  age  of  trees  and  size  of 
trees,  nor  does  it  reflect  seasonal  variations.  With  this  system  old, 
large,  but  low  producing  trees  and  young,  small  but  good  producing 
trees  are  classed  together. 

A  still  better  system  is  that  of  estimating  the  crop  for  each  tree 
in  terms  of  percentage  of  a  theoretically  perfect  or  hundred  per 
cent  crop.  This  system  has  been  used  by  a  few  growers  who  have 
found  it  quite  satisfactory.  In  using  it  the  grower  bears  in  mind 
what  he  considers  a  full  or  maximum  crop  for  each  tree,  and  the 
record  taken  down  represents  the  percentage  of  this  theoretically 
full  crop  which  the  tree  is  actually  carrying.  If  the  tree  has  half  a 
crop  the  figure  five  is  used  to  indicate  that  fact ;  if  a  full  crop,  ten, 
and  so  on.  This  method  takes  care  of  the  factors  of  size  and  age 
relatively  well  but  has  too  many  divisions  for  great  accuracy  with 
the  average  grower.  Moreover,  it  does  not  consider  seasonal  varia- 
tion in  yield  due  to  uncontrollable  weather  conditions  such  as  a  heat 
wave  during  the  period  when  the  crop  is  "setting,"  low  winter 
temperatures  and  other  factors. 

A  much  simpler  system,  and  the  one  herein  recommended,  is 
the  arbitrary  fixing  of  three  or  five  classes  of  trees  according  to 
relative  production,  taking  into  consideration  a  normal  full  crop  for 
the  year.  Where  only  three  classes  are  desired,  the  numerals  1,  2, 
and  3  may  be  used  to  designate  poor,  medium,  and  good  production, 
respectively.  If  further  division  into  five  classes  is  desired  as  a  means 
of  more  detailed  analysis  of  environmental  factors,  the  following  are 
suggested : 

1.  Very  poor. 

2.  Poor. 

3.  Medium    (Fair). 

4.  Good. 

5.  Very  good. 

This  system,  it  is  believed,  is  more  accurate  than  either  of  the 
two  systems  previously  mentioned,  and  in  addition  is  simpler  and 
more  readily  used.  Each  tree  is  estimated  on  the  basis  of  its  size 
(which  usually  indicates  age  as  well)   and  with  regard  to  a  normal 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


full   crop   for  the  year,   considering  general   factors   of   a   climatic 
character. 

When  to  Make  Production  Estimates. — In  the  case  of  orange  vari- 
eties, production  estimate  records  are  necessary  only  once  a  year. 
They  should  not  be  made  until  the  fruit  is  practically  mature  and 
ordinarily  should  be  taken  just  before  picking  begins.  The  accuracy 
of  the  operation,  however,  depends  largely  upon  the  judgment  of 
the  person  making  the  estimates,  and  the  work  should  therefore  be 
done  at  a  period  when  the  fruit  shows  up  well  and  before  conditions 
causing  the  loss  of  a  part  of  the  crop  by  dropping  of  the  fruit  may 


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Fig.  4. — A  suggested  form  for  keeping  estimate  production  records  where 
the  chart  form  is  not  desired.  Estimates  may  be  in  boxes,  percentage  of 
full  crop,  or  in  terms  of  a  comparison  with  a  full  crop  for  the  year.  The 
latter  system  is  shown  and  is  recommended. 

occur.  With  Navel  oranges,  the  period  December  to  March  is  recom- 
mended. For  Valencia  oranges  the  estimates  should  be  made  early 
in  the  season,  preferably  between  April  15  and  June  1. 

In  the  case  of  lemons  it  is  necessary  to  record  production  estimates 
twice  a  year.  The  best  periods  for  doing  this  vary  somewhat  in 
different  districts  but  are  in  general  November  to  January  and  April 
to  June. 

Estimate  Production  Record  Forms. — Simple  forms  for  the  keep- 
ing of  estimate  production  records  are  important.  The  data  neces- 
sary are  the  row  and  tree  number,  and  space  for  keeping  production 
records  for  four  or  five  years.  Production  records  for  four  years 
it  is  believed  are  ample  for  purposes  of  orchard  analysis.    Simple  forms 


Circular  266] 


ANALYZING   THE  CITRUS   ORCHARD 


kept  in  permanent  record  books  may  be  used.  (fig.  4.)  The  pro- 
duction record  may  be  combined  with  the  tree  identity  tag,  (fig.  3) 
or  records  may  be  kept  on  an  orchard  chart.  The  latter  system  has 
advantages,  especially  where  the  acreage  is  not  large,  in  that,  as 
will  be  brought  out  later,  such  a  chart  may  be  used  both  as  production 
record  and  as  distribution  chart,  thus  eliminating  the  necessity  of 


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Fig.  5. — A  chart  form  of  production  record  which  also  serves  as  a  distri- 
bution chart  when  the  production  estimates  are  shown  in  different  colors. 
Each  heavy  square  represents  a  tree.  The  smaller  squares  provide  for  four 
years'  records.  This  system  of  keeping  production  records  is  recommended. 
Key:  1  =  very  poor;  2  =  poor;  3  =  medium  (fair) ;  4  =  good  and  5  =  very  good. 


transferring  production  data  or  preparing  a  separate  distribution 
chart.  The  form  of  chart  recommended  is  that  shown  in  figure  5. 
Each  tree  is  represented  by  a  square  which  is  divided  into  four  parts, 
thus  providing  for  four  years'  records.  The  method  of  division  of 
the  square  suggested  is  recommended  as  furnishing  a  more  satis- 
factory distribution  chart  when  completed,  than  any  method  yet 
devised. 


10  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 


SEGREGATION  INTO  GEOUPS  ACCOEDING  TO  PRODUCTION 

On  the  basis  of  a  single  year's  production  records,  the  trees  may 
be  grouped  in  classes  according  to  production,  although  it  is  probable 
that  such  groupings  cannot  be  regarded  as  more  than  indicative 
until  production  records  for  three  or  four  years  are  available.  The 
latter  period  is  recommended  in  the  belief  that  four  years  of  com- 
parative production  estimates  is  sufficient  upon  which  to  proceed 
with  an  analysis  of  the  orchard. 

When  such  records  have  been  taken  and  averages  for  the  period 
computed,  the  trees  may  be  arranged  in  classes  according  to  pro- 
duction. For  all  practical  purposes  only  three  classes  are  necessary, 
although  the  variation  curve  derived  from  segregating  the  trees  into 
a  larger  number  of  classes  is  decidedly  significant  in  indicating  the 
relative  efficiency  of  the  orchard.  The  grower  is  primarily  inter- 
ested, however,  in  only  three  classes  of  trees :  those  failing  to  make  a 
return  equal  to  the  amount  expended  in  their  care,  usually  referred  to 
as  "boarders";  those  producing  sufficient  fruit  to  approximately  meet 
production  costs  but  not  returning  a  profit,  commonly  called  "self- 
supporters ; ' '  and  those  trees  making  a  return  in  amount  larger  than 
their  share  of  production  costs,  which  may  be  designated  as  "profit- 
returners.  ' ' 

Orchard  Efficiency. — Obviously,  trees  which  have  consistently  pro- 
duced very  poor  or  poor  crops  (classes  1  and  2  in  the  five  class 
estimate  production  record  system)  are  not  returning  sufficient  in- 
come to  balance  production  costs.  It  is  equally  certain  that  the  profits 
returned  from  the  orchard  are  derived  from  those  trees  producing 
good  or  very  good  crops  (classes  4  and  5).  Trees  producing  fair 
crops  (class  3)  may  then  be  regarded  as  on  the  average  making 
returns  approximately  equal  to  costs,  or  in  other  words,  self-support- 
ingly  only.  On  the  basis  of  these  classes  the  grower  is  in  a  position 
to  determine  quite  accurately  the  relative  efficiency  of  his  orchard 
in  terms  of  the  percentages  of  trees  which  are  carried  at  a  loss,  are 
merely  self-supporting,  and  actually  return  a  profit.  The  results 
of  segregation  into  classes  according  to  these  recommendations  as 
secured  from  three  orchards  analyzed  are  presented  in  table  1. 

It  will  be  noted  that  even  in  the  case  of  an  outstandingly  profitable 
orchard,  segregation  of  the  trees  into  these  classes  shows  that  approxi- 
mately one  tree  in  three  is  either  only  self-supporting  or  is  actually 
carried  at  a  loss.  In  the  average  orchard  it  is  believed  that  the  per- 
centage of  such  trees  is  nearer  one-half. 


Circular  266] 


ANALYZING   THE  CITRUS   ORCHARD 


11 


TABLE  1 

Percentage   of   Non-Profitable,   Self-Supporting,    and   Profitable   Trees 
Three  Different  Citrus  Orchards  as  Shown  by  Analysis 


in 


Percentage  of  unprofitable  trees 
Percentage  of  self-supporting  trees 
Percentage  of  profitable  trees 
Total  number  of  trees 


Orchard  V 

13.0 
19.0 
68.0 
5736 


Orchard  2 
14.0 
32.5 
53.5 

800 


Orchard  3 
32.0 
42.0 
26.0 
1525 


Fig.  6. — This  orchard  has  made  net  returns  exceeding  $500  per  acre  per  year 
for  the  past  four  years.  Notwithstanding  this  fact,  analysis  shows  that  only 
68  per  cent  of  the  trees  are  returning  a  profit. 


DISTRIBUTION  IN  THE  ORCHARD  ACCORDING  TO  PRODUCTION 

Having  ascertained  the  relative  efficiency  of  the  orchard  as  shown 
by  segregating  the  trees  into  three  main  groups  according  to  pro- 
duction, the  practical  consideration  is  to  determine  if  possible  the 
causes  of  the  consistent  variation  in  yield  used  as  the  basis  for  such 
segregation.  Is  it  possible  to  bring  the  low  producing  and  medium 
producing  trees  up  to  the  average  of  the  group  returning  profits? 
Does  consistent  low  or  medium  production  demonstrated  over  a  period 


*This  orchard  has  produced  net  returns  of  over  $500  per  acre  for  a  period 
of  years,      (fig.  6.) 


12  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

of  years  mean  inherent  low  or  medium  producing  capacity  ?  At  this 
point  in  the  analysis  these  and  other  questions  of  a  similar  character 
should  occur  to  the  thoughtful  grower. 

Consistent  Performance  vs.  Inherent  Capacity. — In  the  majority 
of  cases  where  growers  have  reached  this  point  in  orchard  analysis, 
the  conclusion  has  been  hastily  arrived  at  that  consistent  low  pro- 
duction at  least,  indicates  inherent  low  fruit  bearing  capacity.  In 
many  cases  trees  of  this  class  have  either  been  removed  or  top-worked, 
frequently  with  the  result  that  the  new  trees  or  top -worked  trees  have 
failed  to  do  better  than  the  original  trees.  The  fact  is  that  consistent 
low  production  does  not  necessarily  mean  low  production  from 
inherent  causes.  In  the  majority  of  cases  low  production  is  the  pro- 
duct of  environmental  factors,  which  may  be  either  wholly  or  par- 
tially remedied. 

The  Distribution  Chart. — Much  valuable  information  relative  to 
the  causes  for  consistent  medium,  and  low  production  may  be  had 
from  a  study  of  the  distribution  of  the  trees  in  the  orchard  according 
to  yield.  This  is  most  readily  visualized  by  means  of  a  distribution 
chart  on  which  the  three  classes  of  trees  as  above  referred  to  are 
shown  in  different  colors.  A  study  of  the  distribution  chart  furn- 
ishes invaluable  information  as  to  the  causes  and  remedies  for  con- 
sistent yield  variation. 

In  the  majority  of  cases  it  will  be  found  that  the  trees  belonging 
to  the  three  classes  are  arranged  in  groups,  bands,  zones,  or  areas, 
instead  of  being  scattered  here  and  there  according  to  the  law  of 
chance.  Such  being  the  case,  it  is  obvious  that  there  must  be  one 
or  more  general  factors  affecting  all  the  trees  in  a  given  group  or 
area,  responsible  for  and  reflected  in  the  production.  Such  factors 
are  therefore  outside  the  trees  themselves  and  of  necessity  must  be 
environmental  in  nature. 

If,  however,  the  trees  are  found  distributed  by  classes  without 
any  apparent  relation  one  to  another,  such  as  would  occur  according 
to  the  law  of  chance,  the  inference  is  reasonable  that,  unless  impaired 
by  pests  or  diseases,  the  causes  for  consistent  differences  in  yield  lie 
within  the  trees  themselves  and  as  such  are  inherent. 

The  making  of  a  satisfactory  distribution  chart  is  therefore  a  matter 
of  the  greatest  importance  to  the  grower,  for  it  is  necessary  for  him 
to  know  the  causes  responsible  for  consistent  yield  variation  in  his 
orchard  in  order  that  the  proper  steps  may  be  taken  to  remedy  them. 
Environmental  causes  for  yield  differences  may  be  possible  to  correct 
by  means  of  changes  in  orchard  management  practices.  Inherent 
causes  may  be  impossible  to  correct,  requiring  the  removal  of  trees 
or  top-working  them  to  more  productive  strains. 


Circular  266] 


ANALYZING   THE  CITRUS   ORCHARD 


13 


Making  the  Distribution  Chart. — Different  methods  may  be  used 
in  making  the  distribution  chart.  The  important  matter  is  to  visu- 
alize the  distribution  of  the  trees  in  the  orchard  according  to  whether 
they  are  low  producers,  medium  producers,  or  good  producers.  This 
may  be  done  by  charting  the  orchard,  with  each  tree  represented 
by  a  small  square,  and  coloring  each  square  according  to  the  four 


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Fig.  7. — Distribution  chart  made  up  in  solid  colors.  The  black  squares 
represent  unprofitable  trees  (boarders) ;  the  cross  lined  squares,  self  support- 
ing trees;  and  the  white  squares,  profitable  trees.  Note  the  zonal  groupings 
indicating  environmental  causes. 


year  average  production  record  made  by  the  tree  it  represents, 
(fig.  7.)  This  requires  considerable  work,  however.  The  same  re- 
sults may  be  had  where  production  estimates  are  recorded  on  the 
orchard  chart,  by  inking  in  the  pencil  records  in  three  contrasting 
colors,  classes  1  and  2  in  one  color,  class  3  in  another,  and  classes 
4  and  5  in  still  another,  (fig.  8.)  In  case  the  latter  system  is  used, 
significant  distribution  groupings  may  be  established  at  the  end  of 


14 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


the  first  year  of  record  keeping  by  merely  inking  in  the  production 
records.  Each  year  these  groupings  will  become  more  clearly  out- 
lined as  further  records  are  inked  in. 

Environmental  Factors. — Of  the  various  environmental  factors 
which  may  be  reflected  in  tree  yields,  those  related  to  soil  conditions 
are  by  far  the  most  important.  Unfavorable  soil  moisture  conditions 
in  all  probability  constitute  the  most  common  environmental  cause 
of  poor  yields.     The  marked  variations  in  soil  texture  which  occur 


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Fig.  8. — Portion  of  distribution  chart  and  production  record  showing  esti- 
mate records  in  different  colors.  Part  of  same  orchard  shown  in  figure  7. 
Numerals  1  and  2  represent  unprofitable  trees;  3,  self-supporting  trees;  and 
numerals  4  and  5,  profitable  trees.   This  form  of  distribution  chart  is  recommended. 


Circular  266]  ANALYZING  THE  CITRUS  ORCHARD  15 

within  comparatively  small  areas  are  well  known  to  citrus  tree  growers. 
The  effects  of  such  variations  on  soil  moisture  conditions,  and  espe- 
cially the  importance  of  adapting  the  irrigation  practice  to  the  soil 
requirements,  however,  have  not  been  sufficiently  appreciated.  Dis- 
tribution charts  frequently  show  broad  bands  of  low  producing  trees 
extending  across  either  the  upper  or  the  lower  ends  of  blocks  of  trees, 
and  in  some  cases  across  both  ends.  The  occurrence  of  such  almost 
invariably  reflects  improper  irrigation  practice,  the  irrigation  fur- 
rows generally  being  found  to  be  too  long  for  efficient  penetration 
of  the  irrigation  water.  In  the  case  of  the  heavier  soil  types,  the 
trees  at  the  lower  ends  of  the  furrows  commonly  do  not  receive  enough 
water,  which  is  strikingly  visualized  on  the  distribution  chart  in  a 
band  of  low  yielding  trees.  On  the  lighter  soils  the  reverse  may  be 
true,  the  trees  at  the  upper  ends  of  the  furrows  receiving  too  much 
water  and  suffering  both  from  the  lack  of  soil  aeration  and  from  the 
leaching  down  below  the  root  feeding  area  of  the  soluble  nitrates. 
In  some  cases,  both  conditions  are  found,  a  band  of  low  producing 
trees  occurring  at  both  the  upper  and  the  lower  ends  of  the  furrows. 
Improper  irrigation  practice  may  also  show  up  in  irregularly  shaped 
areas,  reflecting  spotted  soil  conditions. 

Variations  in  soil  fertility  are  frequently  responsible  for  poor 
yielding  areas.  Distribution  charts  have  brought  out  strikingly  cer- 
tain low  yielding  areas  which  on  further  analysis  have  been  found  to 
coincide  with  elevations  from  which  the  top  soil  was  removed  at 
the  time  the  land  was  levelled  and  prior  to  the  planting  of  the  trees. 
In  a  number  of  such  cases,  resurfacing  these  areas  has  resulted  in 
a  marked  improvement  in  vigor  and  productivity  on  the  part  of  the 
trees.  Distribution  charts  rather  frequently  direct  attention  to  areas 
where  examination  reveals  the  fact  that  the  soil  is  much  lighter  in 
texture  or  shallower  in  depth  than  in  the  rest  of  the  orchard,  and 
although  the  irrigation  practice  may  be  adapted  to  the  soil  type, 
and  soil  moisture  conditions  may  be  satisfactory,  the  trees  are  pre- 
vailingly low  in  production.  Under  such  conditions,  increased  fer- 
tilizer applications  have  usually  caused  marked  improvement  in  yield. 

In  general,  the  first  soil  factor  to  examine  is  moisture.  If  mois- 
ture conditions  are  favorable,  or  after  they  have  been  made  so.  then 
the  question  of  fertility  should  be  analyzed.  In  the  majority  of  cases, 
however,  the  two  will  be  found  rather  intimately  associated  in  their 
effects  on  tree  yield.  One  of  the  most  interesting  examples  illustrat- 
ing the  close  relation  of  the  two  is  the  striking  effect  of  windbreaks 
which  the  distribution  chart  usually  shows. 


16 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


Environmental  factors  which  should  not  be  overlooked  are  topo- 
graphical conditions  which  cause  frost  "pockets"  or  "channels," 
and  areas  where  pests  or  diseases  are  localized. 

The  means  of  modifying  or  overcoming  these  environmental  factors 
are  naturally  suggested  by  the  character  of  the  factor  or  factors 
which  on  analysis  are  found  to  be  responsible  for  yield  variation. 


Fig.  9. — Common  type  of  uncongenial  lemon  bud-union, 
responsible  for  many  unprofitable  trees. 


An  inherent  cause 


The  important  matter,  however,  is  to  analyse  the  areas  which  the 
distribution  chart  reveals,  and  on  the  basis  of  what  is  found,  to  apply 
measures  calculated  to  increase  tree  yields. 

Inherent  Factors. — The  principal  inherent  factors  limiting  yields 
are  the  character  of  the  stock  on  which  the  tree  is  propagated  and 
the  inherent  fruit-bearing  capacity  of  the  parent  tree  from  which  the 
bud-wood  used  in  propagation  was  taken. 


Circular  266]  ANALYZING   THE  CITRUS   ORCHARD  17 

It  is  well  known  that  there  is  much  variation  in  the  stocks  on  which 
citrus  trees  are  propagated.  A  certain  percentage  of  the  seedlings 
prove  to  be  unsatisfactory  for  various  reasons,  principally  slow  growth 
and  unsatisfactory  bud  union  (fig.  9).  While  many  of  these  are 
discarded  in  the  nursery,  some  are  not  detected  and  eventually  are 
planted  in  the  orchards.  These  trees  rarely  prove  satisfactory  in 
production.  Many  of  them  fail  to  grow  properly  and  become  under- 
sized and  unprofitable  trees. 

It  is  also  well  known  that  certain  stocks,  notably  the  trifoliate, 
usually  exert  a  dwarfing  effect  on  most  varieties.  While  trees  propa- 
gated on  this  stock  may  bear  heavy  crops,  the  small  size  of  the  trees 
usually  renders  them  unprofitable. 

At  the  present  time  the  only  practice  which  can  be  recommended 
is  the  pulling  out  of  such  trees  and  their  replacement.  Inarching, 
using  seedlings  of  more  desirable  stocks,  may  eventually  be  found  to 
be  a  successful  method  of  stimulating  trees  of  this  character  to  satis- 
factory growth  and  production.  At  present,  however,  the  use  of 
this  method  for  such  purposes  is  purely  experimental. 

In  cases  where  the  stock  is  satisfactory  and  analysis  fails  to 
reveal  an  environmental  factor  responsible  for  low  production,  it 
may  be  concluded  that  the  tree  itself  represents  an  inherently  low 
producing  strain,  several  of  which  are  known  to  exist.  The  recom- 
mended treatment  for  such  trees  is  top-working,  using  bud-wood 
taken  from  trees  of  known  high  yielding  character.  The  advisability 
of  top-working  lemon  trees,  however,  especially  to  orange  varieties, 
is  seriously  questioned  by  many  growers  of  long  experience. 

THE  TREE  HISTORY  RECORD 

As  a  means  of  having  available  at  all  times,  accurate  information 
as  to  the  condition  of  each  tree  in  the  orchard,  the  keeping  of  an 
individual  tree  history  record  is  invaluable.  By  means  of  such  rec- 
ords the  grower  is  enabled  to  control  all  factors  of  a  disease  or  pest 
control  nature  before  the  injury  from  such  has  progressed  to  the 
point  where  decreased  productivity  results  (fig.  10).  Such  records 
may  also  be  used  to  record  other  data  of  importance  such  as  the  age 
of  the  trees,  history  with  respect  to  top-working,  disease  treatment 
and  pest  control,  all  of  which  are  helpful  in  correctly  interpreting 
analyses  of  the  type  herein  suggested. 

Tree  Inspection. — The  data  necessary  for  the  keeping  of  an  indi- 
vidual tree  history  record  should  be  taken  at  least  once  a  year  and  twice 
a  year  is  recommended  for  the  first  year  or  two  after  the  keeping  of 


18 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


such  records  is  started.  Each  tree  should  receive  a  careful  inspection, 
suitable  notes  being  taken  to  show  conditions  which  should  receive 
immediate  attention.  These  records  should  be  summarized  accord- 
ing" to  the  character  of  the  treatment  necessary,  and  arrangements 
made  to  treat  the  trees  at  the  proper  period. 


Fig.  10. — A  severe  case  of  orange  scalybark  of  long  standing.  Semi-an- 
nual or  annual  tree  inspection  and  the  keeping  of  a  tree  history  record  would 
have  indicated  this  condition  while  the  disease  was  in  the  incipient  stages  and 
eradication    comparatively   simple. 


The  use  of  such  records  not  only  saves  time  in  locating  the  trees 
requiring  treatment,  a  most  important  item  in  itself,  but  also  reminds 
the  owner  of  the  importance  and  necessity  of  individual  tree  care, 
as  a  means  toward  greater  efficiency. 

The  Tree  History  Record  Form. — The  tendency  for  the  grower 
starting  a  system  of  keeping  tree  history  records  is  to  take  down 
much  more  information  concerning  the  condition  of  each  tree  than 


Circular  266] 


ANALYZING   THE  CITRUS   ORCHARD 


19 


is  necessary  or  desirable.  The  key-note  to  a  satisfactory  system  of 
tree  history  record  keeping  is  simplicity.  It  should  be  assumed  that 
conditions  of  disease  or  pest  injury  noted  will  receive  treatment, 
which  renders  it  unnecessary  to  indicate  either  the  stage  or  the 
severity  of  the  condition.  The  treatment  itself  is  the  important 
matter;  consequently  it  is  not  necessary  even  to  distinguish  between 
the  different  classes  of  diseases  or  conditions  which  require  the  same 


Block    No  -6 
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Fig.   11. — Becommended  type   of  tree  history   record  form 


or  similar  treatment.  To  illustrate:  Brown  rot  gum  disease,  lemon 
shell-bark,  gray  mould  gum  disease,  and  scalybark,  all  require  similar 
treatment  and  may  therefore  be  grouped  together  under  the  same  sym- 
bol ;  severe  oil  injury,  foot  rot,  and  gopher  injury,  present  to  the  degree 
of  partially  or  entirely  girdling  the  tree,  all  require  approximately 
the  same  treatment,  inarching,  and  may  conveniently  be  grouped 
under  the  same  symbol.  When  inspection  indicates  that  the  condi- 
tion has  been  overcome,  this  fact  may  be  shown  by  the  proper  symbol 
with  a  line  drawn  through  it. 


20  UNIVERSITY    OF   CALIFORNIA EXPERIMENT    STATION 

The  data  needed  on  the  tree  history  record  are  essentially  the 
row  number  and  tree  number  (tree  identity  and  location),  the  date 
of  planting  (especially  important  for  replants),  and  spaces  for  re- 
cording" treatments  required  as  indicated  at  either  an  annual  or  semi- 
annual inspection.     A  satisfactory  form  is  that  shown  in  figure  11. 

CONCLUSION 

By  means  of  conducting  the  type  of  efficiency  orchard  analysis 
described  in  this  circular,  together  with  the  keeping  of  simple  tree 
history  records,  it  is  believed  the  citrus  grower  can  furnish  himself 
with  extremely  helpful  information  relative  to  ways  and  means  for 
increasing  his  returns.  The  grower  may  determine  for  himself  the 
relative  efficiency  of  his  orchard,  and  also  the  nature  of  the  causes 
contributing  thereto.  He  is  then  in  a  position  to  analyse  these  and 
to  apply  the  proper  remedial  measures. 

SUMMAEY 

Three  sets  of  factors  are  operative  in  determining  the  production 
of  citrus  orchards:  the  cultural  practices  used,  the  inherent  qualities 
of  the  trees,  and  the  orchard  environment. 

Of  these,  the  first  two  have  received  considerable  attention.  The 
third  has  been  largely  neglected.  It  is  a  factor  of  considerable  im- 
portance and  deserving  of  much  more  attention. 

A  means  of  visualizing  the  importance  of  this  factor  and  its  rela- 
tion to  the  other  two  is  described  in  this  circular. 

It  consists  of  an  orchard  efficiency  analysis  which  emphasizes  the 
tree  as  the  ultimate  production  unit  of  the  citrus  orchard  and  includes 
the  following  steps : 

1.  Establishing  tree  identities. 

2.  Keeping  simple  estimate  production  records. 

3.  Segregating  the  trees  into  classes  according  to  yields. 

4.  Determining  the  efficiency  of  the  orchard. 

5.  Determining  the  distribution  of  the  trees  in  the  orchard  accord- 
ing to  yields. 

6.  Ascertaining  the  causes  of  consistent  yield  variation  as  to 
whether  environmental  or  inherent  in  character. 

7.  Analysing  the  causes  determined  and  applying  proper  remedial 
measures. 

8.  Keeping  a  simple  individual  tree  history  record  as  an  aid  to 
increased  tree  efficiency. 


STATION  PUBLICATIONS  AVAILABLE  FOR  FREE  DISTRIBUTION 


BULLETINS 

No.  No. 

253.   Irrigation    and    Soil   Conditions   in   the  334. 
Sierra  Nevada  Foothills,  California. 

261.  Melaxuma    of    the    Walnut,     "Juglans  335. 

regia." 

262.  Citrus   Diseases   of   Florida   and   Cuba  336. 

Compared  with  those  of  California. 

263.  Size  Grades  for  Ripe  Olives.  337. 

268.   Growing  and  Grafting  Olive  Seedlings.  339. 

270.  A  Comparison  of  Annual  Cropping,  Bi- 
ennial Cropping  and  Green  Manures  341. 
on  the  Yield  of  Wheat.  343. 

273.  Preliminary  Report  on  Kearney  Vine-  344. 

yard  Experimental  Drain. 

275.  The  Cultivation  of  Belladonna  in  Cali-  346. 

fornia.  347. 

276.  The    Pomegranate. 

278.  Grain   Sorghums.  348. 

279.  Irrigation  of  Rice  in  California.  349. 

280.  Irrigation  of  Alfalfa  in  the  Sacramento 

Valley.  350. 

283.  The  Olive  Insects  of  California.  35l! 

285.  The  Milk  Goat  in  California.  352. 

286.  Commercial    Fertilizers. 

287.  Vinegar  from  Waste  Fruits.  353. 
294.  Bean  Culture  in  California.  354. 
298.  Seedless  Raisin  Grapes.  355. 
304.  A  Study  of  the  Effects  of  Freezes  on  357. 

Citrus   in   California. 
308.   I.  Fumigation  with  Liquid  Hydrocyanic 

Acid.  II.  Physical  and  Chemical  Prop-  358. 

erties  of  Liquid  Hydrocyanic  Acid. 

312.  Mariout  Barlev.  359. 

313.  Pruning  Young   Deciduous  Fruit  Trees.  360. 
317.   Selections   of   Stocks  in   Citrus   Propa- 
gation. 361, 

319.   Caprifigs  and  Caprification. 

321.   Commercial  Production  of  Grape  Syrup.  362. 

324.  Storage  of  Perishable  Fruit  at  Freezing  363 

Temperatures. 

325.  Rice  Irrigation  Measurements  and  Ex-  364 

periments     in      Sacramento     Valley, 
1914-1919.  365 

328.   Prune  Growing  in  California. 

331.  Phylloxera-Resistant   Stocks. 

332.  Walnut  Culture  in  California. 


Preliminary  Volume  Tables  for  Second- 
Growth   Redwoods. 

Cocoanut    Meal    as    a    Feed    for    Dairy 
Cows  and   Other  Livestock. 

The   Preparation   of   Nicotine   Dust   as 
an  Insecticide. 

Some  Factors  of  Dehydrater  Efficiency. 

The  Relative  Cost  of  Making  Logs  from 
Small    and    Large   Timber. 

Studies  on  Irrigation  of  Citrus  Groves. 

Cheese  Pests  and  Their  Control. 

Cold  Storage  as  an  Aid  to  the  Market- 
ing of  Plums. 

Almond    Pollination. 

The  Control  of  Red  Spiders  in  Decidu- 
ous  Orchards. 

Pruning  Young  Olive  Trees. 

A    Study    of    Sidedraft    and    Tractor 
Hitches. 

Agriculture  in  Cut-over  Redwood  Lands. 

California  State  Dairy  Cow  Competition. 

Further  Experiments  in  Plum  Pollina- 
tion. 

Bovine  Infectious  Abortion. 

Results  of  Rice  Experiments  in    1922. 

The  Peach  Twig  Borer. 

A    Self-mixing    Dusting    Machine 
Applying      Dry       Insecticides 
Fungicides. 

Black     Measles,     Water    Berries, 
Related    Vine    Troubles. 

Fruit  Beverage  Investigations. 

Gum  Diseases  of  Citrus  Trees  in  Cali- 
fornia. 

Preliminary   Yield   Tables    for    Second 
Growth  Redwood. 

Dust  and  the  Tractor  Engine. 

The  Pruning  of  Citrus  Trees  in  Cali- 
fornia. 

Fungicidal    Dusts    for   the    Control    of 
Bunt. 

Avocado  Culture  in  California. 


for 
and 


and 


No. 

70.  Observations  on  the  Status  of  Corn 
Growing  in  California. 

82.  The  Common  Ground  Squirrel  of  Cali- 
fornia. 

87.  Alfalfa. 

110.  Green  Manuring  in  California. 

111.  The  Use  of  Lime  and  Gypsum  on  Cali- 

fornia Soils. 
113.  Correspondence  Courses  in  Agriculture. 
117.  The    Selection    and    Cost    of    a    Small 

Pumping  Plant. 
136.   Melilotus    xndica    as    a    Green-Manure 

Crop  for  California. 
127.   House  Fumigation. 

144.   Oidium  or  Powdery  Mildew  of  the  Vine. 
148.   "Lungworms." 

151.  Feeding  and  Management  of  Hogs. 

152.  Some    Observations  on  the  Bulk    Hand- 

ling of  Grain   in   California. 
155.   Bovine  Tuberculosis. 
157.   Control  of  the  Pear  Scab. 

159.  Agriculture   in   the   Imperial   Valley. 

160.  Lettuce  Growing  in  California. 

161.  Potatoes  in  California. 


CIRCULARS 
No. 

165. 


166. 
167. 
170. 

172. 
173. 

174. 
175. 

178. 
179. 

182. 

183. 
184. 
188. 
190. 
193. 
198. 
199. 


Fundamentals   of    Sugar   Beet   Culture 

under  California  Conditions. 
The  County  Farm  Bureau. 
Feeding  Stuffs  of  Minor  Importance. 
Fertilizing  California  Soils  for  the  1918 

Crop. 
Wheat  Culture. 
The    Construction    of    the    Wood-Hoop 

Silo. 
Farm   Drainage  Methods. 
Progress  Report  on  the  Marketing  and 

Distribution   of  Milk. 
The  Packing  of  Apples  in  California. 
Factors    of    Importance    in    Producing 

Milk  of  Low  Bacterial  Count. 
Extending  the  Area  of  Irrigated  Wheat 

in    California    for   1918. 
Infectious  Abortion  in  Cows. 
A  Flock  of  Sheep  on  the  Farm. 
Lambing  Sheds. 

Agriculture  Clubs   in   California. 
A  Study  of  Farm  Labor  in  California. 
Syrup   from    Sweet   Sorghum. 
Onion  Growing  in  California. 


CIRCULARS — Continued 


No.  No. 

201.  Helpful  Hints  to   Hog  Raisers.  237. 

202.  County    Organizations   for   Rural   Fire 

Control.  238. 

203.  Peat  as  a  Manure  Substitute.  239. 
205.   Blackleg. 

^06.   Jack  Cheese.  240. 

208.  Summary  of  the  Annual  Reports  of  the 

Farm  Advisors  of  California.  241. 

209.  The  Function  of  the  Farm  Bureau. 

210.  Suggestions  to  the  Settler  in  California.  242. 
212.   Salvaging  Rain-Damaged  Prunes.  244. 

214.  Seed  Treatment  for  the  Prevention  of  245. 

Cereal   Smuts.  247. 

215.  Feeding  Dairy  Cows  in  California.  248. 

217.  Methods    for   Marketing   Vegetables   in 

California.  249. 

218.  Advanced    Registry    Testing    of    Dairy  250. 

Cows. 

219.  The  Present  Status  of  Alkali.  251. 
224.   Control    of    the    Brown    Apricot    Scale 

and  the  Italian  Pear  Scale  on  Decid- 
uous Fruit  Trees.  252. 

228.  Vineyard   Irrigation  in   Arid  Climates.  253. 

230.   Testing  Milk,    Cream,    and    Skim   Milk  254. 

for  Butterfat. 

232.  Harvesting    and    Handling    California  255. 

Cherries  for  Eastern  Shipment. 

233.  Artificial  Incubation.  256. 

234.  Winter  Injury  to  Young  Walnut  Trees  257. 

during  1921-22.  258. 

235.  Soil  Analysis  and  Soil  and  Plant  Inter-  259. 

relations.  260. 

236.  The  Common  Hawks  and  Owls  of  Cali- 

fornia  from    the     Standpoint  of  the 
Rancher. 


Directions  for  the  Tanning  and  Dress- 
ing of  Furs. 

The  Apricot  in  California. 

Harvesting  and  Handling  Apricots  and 
Plums  for  Eastern   Shipment. 

Harvesting  and  Handling  Pears  for 
Eastern   Shipment. 

Harvesting  and  Handling  Peaches  for 
Eastern   Shipment. 

Poultry  Feeding. 

Central  Wire  Bracing  for  Fruit  Trees. 

Vine  Pruning  Systems. 

Colonization   and  Rural  Development. 

Some  Common  Errors  in  Vine  Prunimg 
and  Their  Remedies. 

Replacing  Missing  Vines. 

Measurement  of  Irrigation  Water  on 
the   Farm. 

Recommendations  Concerning  the  Com- 
mon Diseases  and  Parasites  of 
Poultry    in    California. 

Supports  for  Vines. 

Vineyard   Plans. 

The  Use  of  Artificial  Light  to  Increase 
Winter  Egg  Production. 

Leguminous  Plants  as  Organic  Fertil- 
izer in  California  Agriculture. 

The  Control  of  Wild  Morning  Glory. 

The  Small-Seeded  Horse  Bean. 

Thinning  Deciduous  Fruits. 

Pear  By-products. 

A  Selected  List  of  References  Relating 
to  Irrigation  in  California. 


